21605425620 has 96 divisors (see below), whose sum is σ = 61684301952. Its totient is φ = 5648368128.

The previous prime is 21605425609. The next prime is 21605425631. The reversal of 21605425620 is 2652450612.

It is an interprime number because it is at equal distance from previous prime (21605425609) and next prime (21605425631).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 7290259 + ... + 7293221.

It is an arithmetic number, because the mean of its divisors is an integer number (642544812).

Almost surely, 2^21605425620 is an apocalyptic number.

21605425620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21605425620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30842150976).

21605425620 is an abundant number, since it is smaller than the sum of its proper divisors (40078876332).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21605425620 is a wasteful number, since it uses less digits than its factorization.

21605425620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5321 (or 5319 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 33.

The spelling of 21605425620 in words is "twenty-one billion, six hundred five million, four hundred twenty-five thousand, six hundred twenty".